src/libnetdata/eval/eval.c
// SPDX-License-Identifier: GPL-3.0-or-later
#include "../libnetdata.h"
typedef enum __attribute__((packed)) {
EVAL_VALUE_INVALID = 0,
EVAL_VALUE_NUMBER,
EVAL_VALUE_VARIABLE,
EVAL_VALUE_EXPRESSION
} EVAL_VALUE_TYPE;
// ----------------------------------------------------------------------------
// data structures for storing the parsed expression in memory
typedef struct eval_variable {
STRING *name;
struct eval_variable *next;
} EVAL_VARIABLE;
typedef struct eval_value {
EVAL_VALUE_TYPE type;
union {
NETDATA_DOUBLE number;
EVAL_VARIABLE *variable;
struct eval_node *expression;
};
} EVAL_VALUE;
typedef struct eval_node {
int id;
unsigned char operator;
int precedence;
int count;
EVAL_VALUE ops[];
} EVAL_NODE;
struct eval_expression {
STRING *source;
STRING *parsed_as;
NETDATA_DOUBLE result;
int error;
BUFFER *error_msg;
EVAL_NODE *nodes;
void *variable_lookup_cb_data;
eval_expression_variable_lookup_t variable_lookup_cb;
};
// these are used for EVAL_NODE.operator
// they are used as internal IDs to identify an operator
// THEY ARE NOT USED FOR PARSING OPERATORS LIKE THAT
#define EVAL_OPERATOR_NOP '\0'
#define EVAL_OPERATOR_EXPRESSION_OPEN '('
#define EVAL_OPERATOR_EXPRESSION_CLOSE ')'
#define EVAL_OPERATOR_NOT '!'
#define EVAL_OPERATOR_PLUS '+'
#define EVAL_OPERATOR_MINUS '-'
#define EVAL_OPERATOR_AND '&'
#define EVAL_OPERATOR_OR '|'
#define EVAL_OPERATOR_GREATER_THAN_OR_EQUAL 'G'
#define EVAL_OPERATOR_LESS_THAN_OR_EQUAL 'L'
#define EVAL_OPERATOR_NOT_EQUAL '~'
#define EVAL_OPERATOR_EQUAL '='
#define EVAL_OPERATOR_LESS '<'
#define EVAL_OPERATOR_GREATER '>'
#define EVAL_OPERATOR_MULTIPLY '*'
#define EVAL_OPERATOR_DIVIDE '/'
#define EVAL_OPERATOR_SIGN_PLUS 'P'
#define EVAL_OPERATOR_SIGN_MINUS 'M'
#define EVAL_OPERATOR_ABS 'A'
#define EVAL_OPERATOR_IF_THEN_ELSE '?'
// ----------------------------------------------------------------------------
// forward function definitions
static inline void eval_node_free(EVAL_NODE *op);
static inline EVAL_NODE *parse_full_expression(const char **string, int *error);
static inline EVAL_NODE *parse_one_full_operand(const char **string, int *error);
static inline NETDATA_DOUBLE eval_node(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error);
static inline void print_parsed_as_node(BUFFER *out, EVAL_NODE *op, int *error);
static inline void print_parsed_as_constant(BUFFER *out, NETDATA_DOUBLE n);
// ----------------------------------------------------------------------------
// evaluation of expressions
static inline NETDATA_DOUBLE eval_variable(EVAL_EXPRESSION *exp, EVAL_VARIABLE *v, int *error) {
NETDATA_DOUBLE n;
if(exp->variable_lookup_cb && exp->variable_lookup_cb(v->name, exp->variable_lookup_cb_data, &n)) {
buffer_sprintf(exp->error_msg, "[ ${%s} = ", string2str(v->name));
print_parsed_as_constant(exp->error_msg, n);
buffer_strcat(exp->error_msg, " ] ");
return n;
}
*error = EVAL_ERROR_UNKNOWN_VARIABLE;
buffer_sprintf(exp->error_msg, "[ undefined variable '%s' ] ", string2str(v->name));
return NAN;
}
static inline NETDATA_DOUBLE eval_value(EVAL_EXPRESSION *exp, EVAL_VALUE *v, int *error) {
NETDATA_DOUBLE n;
switch(v->type) {
case EVAL_VALUE_EXPRESSION:
n = eval_node(exp, v->expression, error);
break;
case EVAL_VALUE_NUMBER:
n = v->number;
break;
case EVAL_VALUE_VARIABLE:
n = eval_variable(exp, v->variable, error);
break;
default:
*error = EVAL_ERROR_INVALID_VALUE;
n = 0;
break;
}
return n;
}
static inline int is_true(NETDATA_DOUBLE n) {
if(isnan(n)) return 0;
if(isinf(n)) return 1;
if(n == 0) return 0;
return 1;
}
NETDATA_DOUBLE eval_and(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return is_true(eval_value(exp, &op->ops[0], error)) && is_true(eval_value(exp, &op->ops[1], error));
}
NETDATA_DOUBLE eval_or(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return is_true(eval_value(exp, &op->ops[0], error)) || is_true(eval_value(exp, &op->ops[1], error));
}
NETDATA_DOUBLE eval_greater_than_or_equal(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
return isgreaterequal(n1, n2);
}
NETDATA_DOUBLE eval_less_than_or_equal(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
return islessequal(n1, n2);
}
NETDATA_DOUBLE eval_equal(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
if(isnan(n1) && isnan(n2)) return 1;
if(isinf(n1) && isinf(n2)) return 1;
if(isnan(n1) || isnan(n2)) return 0;
if(isinf(n1) || isinf(n2)) return 0;
return considered_equal_ndd(n1, n2);
}
NETDATA_DOUBLE eval_not_equal(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return !eval_equal(exp, op, error);
}
NETDATA_DOUBLE eval_less(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
return isless(n1, n2);
}
NETDATA_DOUBLE eval_greater(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
return isgreater(n1, n2);
}
NETDATA_DOUBLE eval_plus(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
if(isnan(n1) || isnan(n2)) return NAN;
if(isinf(n1) || isinf(n2)) return INFINITY;
return n1 + n2;
}
NETDATA_DOUBLE eval_minus(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
if(isnan(n1) || isnan(n2)) return NAN;
if(isinf(n1) || isinf(n2)) return INFINITY;
return n1 - n2;
}
NETDATA_DOUBLE eval_multiply(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
if(isnan(n1) || isnan(n2)) return NAN;
if(isinf(n1) || isinf(n2)) return INFINITY;
return n1 * n2;
}
NETDATA_DOUBLE eval_divide(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
NETDATA_DOUBLE n2 = eval_value(exp, &op->ops[1], error);
if(isnan(n1) || isnan(n2)) return NAN;
if(isinf(n1) || isinf(n2)) return INFINITY;
return n1 / n2;
}
NETDATA_DOUBLE eval_nop(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return eval_value(exp, &op->ops[0], error);
}
NETDATA_DOUBLE eval_not(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return !is_true(eval_value(exp, &op->ops[0], error));
}
NETDATA_DOUBLE eval_sign_plus(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
return eval_value(exp, &op->ops[0], error);
}
NETDATA_DOUBLE eval_sign_minus(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
if(isnan(n1)) return NAN;
if(isinf(n1)) return INFINITY;
return -n1;
}
NETDATA_DOUBLE eval_abs(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
NETDATA_DOUBLE n1 = eval_value(exp, &op->ops[0], error);
if(isnan(n1)) return NAN;
if(isinf(n1)) return INFINITY;
return ABS(n1);
}
NETDATA_DOUBLE eval_if_then_else(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
if(is_true(eval_value(exp, &op->ops[0], error)))
return eval_value(exp, &op->ops[1], error);
else
return eval_value(exp, &op->ops[2], error);
}
static struct operator {
const char *print_as;
char precedence;
char parameters;
char isfunction;
NETDATA_DOUBLE (*eval)(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error);
} operators[256] = {
// this is a random access array
// we always access it with a known EVAL_OPERATOR_X
[EVAL_OPERATOR_AND] = { "&&", 2, 2, 0, eval_and },
[EVAL_OPERATOR_OR] = { "||", 2, 2, 0, eval_or },
[EVAL_OPERATOR_GREATER_THAN_OR_EQUAL] = { ">=", 3, 2, 0, eval_greater_than_or_equal },
[EVAL_OPERATOR_LESS_THAN_OR_EQUAL] = { "<=", 3, 2, 0, eval_less_than_or_equal },
[EVAL_OPERATOR_NOT_EQUAL] = { "!=", 3, 2, 0, eval_not_equal },
[EVAL_OPERATOR_EQUAL] = { "==", 3, 2, 0, eval_equal },
[EVAL_OPERATOR_LESS] = { "<", 3, 2, 0, eval_less },
[EVAL_OPERATOR_GREATER] = { ">", 3, 2, 0, eval_greater },
[EVAL_OPERATOR_PLUS] = { "+", 4, 2, 0, eval_plus },
[EVAL_OPERATOR_MINUS] = { "-", 4, 2, 0, eval_minus },
[EVAL_OPERATOR_MULTIPLY] = { "*", 5, 2, 0, eval_multiply },
[EVAL_OPERATOR_DIVIDE] = { "/", 5, 2, 0, eval_divide },
[EVAL_OPERATOR_NOT] = { "!", 6, 1, 0, eval_not },
[EVAL_OPERATOR_SIGN_PLUS] = { "+", 6, 1, 0, eval_sign_plus },
[EVAL_OPERATOR_SIGN_MINUS] = { "-", 6, 1, 0, eval_sign_minus },
[EVAL_OPERATOR_ABS] = { "abs(",6,1, 1, eval_abs },
[EVAL_OPERATOR_IF_THEN_ELSE] = { "?", 7, 3, 0, eval_if_then_else },
[EVAL_OPERATOR_NOP] = { NULL, 8, 1, 0, eval_nop },
[EVAL_OPERATOR_EXPRESSION_OPEN] = { NULL, 8, 1, 0, eval_nop },
// this should exist in our evaluation list
[EVAL_OPERATOR_EXPRESSION_CLOSE] = { NULL, 99, 1, 0, eval_nop }
};
#define eval_precedence(operator) (operators[(unsigned char)(operator)].precedence)
static inline NETDATA_DOUBLE eval_node(EVAL_EXPRESSION *exp, EVAL_NODE *op, int *error) {
if(unlikely(op->count != operators[op->operator].parameters)) {
*error = EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS;
return 0;
}
NETDATA_DOUBLE n = operators[op->operator].eval(exp, op, error);
return n;
}
// ----------------------------------------------------------------------------
// parsed-as generation
static inline void print_parsed_as_variable(BUFFER *out, EVAL_VARIABLE *v, int *error) {
(void)error;
buffer_sprintf(out, "${%s}", string2str(v->name));
}
static inline void print_parsed_as_constant(BUFFER *out, NETDATA_DOUBLE n) {
if(unlikely(isnan(n))) {
buffer_strcat(out, "nan");
return;
}
if(unlikely(isinf(n))) {
buffer_strcat(out, "inf");
return;
}
char b[100+1], *s;
snprintfz(b, sizeof(b) - 1, NETDATA_DOUBLE_FORMAT, n);
s = &b[strlen(b) - 1];
while(s > b && *s == '0') {
*s ='\0';
s--;
}
if(s > b && *s == '.')
*s = '\0';
buffer_strcat(out, b);
}
static inline void print_parsed_as_value(BUFFER *out, EVAL_VALUE *v, int *error) {
switch(v->type) {
case EVAL_VALUE_EXPRESSION:
print_parsed_as_node(out, v->expression, error);
break;
case EVAL_VALUE_NUMBER:
print_parsed_as_constant(out, v->number);
break;
case EVAL_VALUE_VARIABLE:
print_parsed_as_variable(out, v->variable, error);
break;
default:
*error = EVAL_ERROR_INVALID_VALUE;
break;
}
}
static inline void print_parsed_as_node(BUFFER *out, EVAL_NODE *op, int *error) {
if(unlikely(op->count != operators[op->operator].parameters)) {
*error = EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS;
return;
}
if(operators[op->operator].parameters == 1) {
if(operators[op->operator].print_as)
buffer_sprintf(out, "%s", operators[op->operator].print_as);
//if(op->operator == EVAL_OPERATOR_EXPRESSION_OPEN)
// buffer_strcat(out, "(");
print_parsed_as_value(out, &op->ops[0], error);
//if(op->operator == EVAL_OPERATOR_EXPRESSION_OPEN)
// buffer_strcat(out, ")");
}
else if(operators[op->operator].parameters == 2) {
buffer_strcat(out, "(");
print_parsed_as_value(out, &op->ops[0], error);
if(operators[op->operator].print_as)
buffer_sprintf(out, " %s ", operators[op->operator].print_as);
print_parsed_as_value(out, &op->ops[1], error);
buffer_strcat(out, ")");
}
else if(op->operator == EVAL_OPERATOR_IF_THEN_ELSE && operators[op->operator].parameters == 3) {
buffer_strcat(out, "(");
print_parsed_as_value(out, &op->ops[0], error);
if(operators[op->operator].print_as)
buffer_sprintf(out, " %s ", operators[op->operator].print_as);
print_parsed_as_value(out, &op->ops[1], error);
buffer_strcat(out, " : ");
print_parsed_as_value(out, &op->ops[2], error);
buffer_strcat(out, ")");
}
if(operators[op->operator].isfunction)
buffer_strcat(out, ")");
}
// ----------------------------------------------------------------------------
// parsing expressions
// skip spaces
static inline void skip_spaces(const char **string) {
const char *s = *string;
while(isspace((uint8_t)*s)) s++;
*string = s;
}
// what character can appear just after an operator keyword
// like NOT AND OR ?
static inline int isoperatorterm_word(const char s) {
if(isspace(s) || s == '(' || s == '$' || s == '!' || s == '-' || s == '+' || isdigit(s) || !s)
return 1;
return 0;
}
// what character can appear just after an operator symbol?
static inline int isoperatorterm_symbol(const char s) {
if(isoperatorterm_word(s) || isalpha(s))
return 1;
return 0;
}
// return 1 if the character should never appear in a variable
static inline int isvariableterm(const char s) {
if(isalnum(s) || s == '.' || s == '_')
return 0;
return 1;
}
// ----------------------------------------------------------------------------
// parse operators
static inline int parse_and(const char **string) {
const char *s = *string;
// AND
if((s[0] == 'A' || s[0] == 'a') && (s[1] == 'N' || s[1] == 'n') && (s[2] == 'D' || s[2] == 'd') && isoperatorterm_word(s[3])) {
*string = &s[4];
return 1;
}
// &&
if(s[0] == '&' && s[1] == '&' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
return 0;
}
static inline int parse_or(const char **string) {
const char *s = *string;
// OR
if((s[0] == 'O' || s[0] == 'o') && (s[1] == 'R' || s[1] == 'r') && isoperatorterm_word(s[2])) {
*string = &s[3];
return 1;
}
// ||
if(s[0] == '|' && s[1] == '|' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
return 0;
}
static inline int parse_greater_than_or_equal(const char **string) {
const char *s = *string;
// >=
if(s[0] == '>' && s[1] == '=' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
return 0;
}
static inline int parse_less_than_or_equal(const char **string) {
const char *s = *string;
// <=
if (s[0] == '<' && s[1] == '=' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
return 0;
}
static inline int parse_greater(const char **string) {
const char *s = *string;
// >
if(s[0] == '>' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_less(const char **string) {
const char *s = *string;
// <
if(s[0] == '<' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_equal(const char **string) {
const char *s = *string;
// ==
if(s[0] == '=' && s[1] == '=' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
// =
if(s[0] == '=' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_not_equal(const char **string) {
const char *s = *string;
// !=
if(s[0] == '!' && s[1] == '=' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
return 1;
}
// <>
if(s[0] == '<' && s[1] == '>' && isoperatorterm_symbol(s[2])) {
*string = &s[2];
}
return 0;
}
static inline int parse_not(const char **string) {
const char *s = *string;
// NOT
if((s[0] == 'N' || s[0] == 'n') && (s[1] == 'O' || s[1] == 'o') && (s[2] == 'T' || s[2] == 't') && isoperatorterm_word(s[3])) {
*string = &s[3];
return 1;
}
if(s[0] == '!') {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_multiply(const char **string) {
const char *s = *string;
// *
if(s[0] == '*' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_divide(const char **string) {
const char *s = *string;
// /
if(s[0] == '/' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_minus(const char **string) {
const char *s = *string;
// -
if(s[0] == '-' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_plus(const char **string) {
const char *s = *string;
// +
if(s[0] == '+' && isoperatorterm_symbol(s[1])) {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_open_subexpression(const char **string) {
const char *s = *string;
// (
if(s[0] == '(') {
*string = &s[1];
return 1;
}
return 0;
}
#define parse_close_function(x) parse_close_subexpression(x)
static inline int parse_close_subexpression(const char **string) {
const char *s = *string;
// )
if(s[0] == ')') {
*string = &s[1];
return 1;
}
return 0;
}
static inline int parse_variable(const char **string, char *buffer, size_t len) {
const char *s = *string;
// $
if(*s == '$') {
size_t i = 0;
s++;
if(*s == '{') {
// ${variable_name}
s++;
while (*s && *s != '}' && i < len)
buffer[i++] = *s++;
if(*s == '}')
s++;
}
else {
// $variable_name
while (*s && !isvariableterm(*s) && i < len)
buffer[i++] = *s++;
}
buffer[i] = '\0';
if (buffer[0]) {
*string = s;
return 1;
}
}
return 0;
}
static inline int parse_constant(const char **string, NETDATA_DOUBLE *number) {
char *end = NULL;
NETDATA_DOUBLE n = str2ndd(*string, &end);
if(unlikely(!end || *string == end)) {
*number = 0;
return 0;
}
*number = n;
*string = end;
return 1;
}
static inline int parse_abs(const char **string) {
const char *s = *string;
// ABS
if((s[0] == 'A' || s[0] == 'a') && (s[1] == 'B' || s[1] == 'b') && (s[2] == 'S' || s[2] == 's') && s[3] == '(') {
*string = &s[3];
return 1;
}
return 0;
}
static inline int parse_if_then_else(const char **string) {
const char *s = *string;
// ?
if(s[0] == '?') {
*string = &s[1];
return 1;
}
return 0;
}
static struct operator_parser {
unsigned char id;
int (*parse)(const char **);
} operator_parsers[] = {
// the order in this list is important!
// the first matching will be used
// so place the longer of overlapping ones
// at the top
{ EVAL_OPERATOR_AND, parse_and },
{ EVAL_OPERATOR_OR, parse_or },
{ EVAL_OPERATOR_GREATER_THAN_OR_EQUAL, parse_greater_than_or_equal },
{ EVAL_OPERATOR_LESS_THAN_OR_EQUAL, parse_less_than_or_equal },
{ EVAL_OPERATOR_NOT_EQUAL, parse_not_equal },
{ EVAL_OPERATOR_EQUAL, parse_equal },
{ EVAL_OPERATOR_LESS, parse_less },
{ EVAL_OPERATOR_GREATER, parse_greater },
{ EVAL_OPERATOR_PLUS, parse_plus },
{ EVAL_OPERATOR_MINUS, parse_minus },
{ EVAL_OPERATOR_MULTIPLY, parse_multiply },
{ EVAL_OPERATOR_DIVIDE, parse_divide },
{ EVAL_OPERATOR_IF_THEN_ELSE, parse_if_then_else },
/* we should not put in this list the following:
*
* - NOT
* - (
* - )
*
* these are handled in code
*/
// termination
{ EVAL_OPERATOR_NOP, NULL }
};
static inline unsigned char parse_operator(const char **string, int *precedence) {
skip_spaces(string);
int i;
for(i = 0 ; operator_parsers[i].parse != NULL ; i++)
if(operator_parsers[i].parse(string)) {
if(precedence) *precedence = eval_precedence(operator_parsers[i].id);
return operator_parsers[i].id;
}
return EVAL_OPERATOR_NOP;
}
// ----------------------------------------------------------------------------
// memory management
static inline EVAL_NODE *eval_node_alloc(int count) {
static int id = 1;
EVAL_NODE *op = callocz(1, sizeof(EVAL_NODE) + (sizeof(EVAL_VALUE) * count));
op->id = id++;
op->operator = EVAL_OPERATOR_NOP;
op->precedence = eval_precedence(EVAL_OPERATOR_NOP);
op->count = count;
return op;
}
static inline void eval_node_set_value_to_node(EVAL_NODE *op, int pos, EVAL_NODE *value) {
if(pos >= op->count)
fatal("Invalid request to set position %d of OPERAND that has only %d values", pos + 1, op->count + 1);
op->ops[pos].type = EVAL_VALUE_EXPRESSION;
op->ops[pos].expression = value;
}
static inline void eval_node_set_value_to_constant(EVAL_NODE *op, int pos, NETDATA_DOUBLE value) {
if(pos >= op->count)
fatal("Invalid request to set position %d of OPERAND that has only %d values", pos + 1, op->count + 1);
op->ops[pos].type = EVAL_VALUE_NUMBER;
op->ops[pos].number = value;
}
static inline void eval_node_set_value_to_variable(EVAL_NODE *op, int pos, const char *variable) {
if(pos >= op->count)
fatal("Invalid request to set position %d of OPERAND that has only %d values", pos + 1, op->count + 1);
op->ops[pos].type = EVAL_VALUE_VARIABLE;
op->ops[pos].variable = callocz(1, sizeof(EVAL_VARIABLE));
op->ops[pos].variable->name = string_strdupz(variable);
}
static inline void eval_variable_free(EVAL_VARIABLE *v) {
string_freez(v->name);
freez(v);
}
static inline void eval_value_free(EVAL_VALUE *v) {
switch(v->type) {
case EVAL_VALUE_EXPRESSION:
eval_node_free(v->expression);
break;
case EVAL_VALUE_VARIABLE:
eval_variable_free(v->variable);
break;
default:
break;
}
}
static inline void eval_node_free(EVAL_NODE *op) {
if(op->count) {
int i;
for(i = op->count - 1; i >= 0 ;i--)
eval_value_free(&op->ops[i]);
}
freez(op);
}
// ----------------------------------------------------------------------------
// the parsing logic
// helper function to avoid allocations all over the place
static inline EVAL_NODE *parse_next_operand_given_its_operator(const char **string, unsigned char operator_type, int *error) {
EVAL_NODE *sub = parse_one_full_operand(string, error);
if(!sub) return NULL;
EVAL_NODE *op = eval_node_alloc(1);
op->operator = operator_type;
eval_node_set_value_to_node(op, 0, sub);
return op;
}
// parse a full operand, including its sign or other associative operator (e.g. NOT)
static inline EVAL_NODE *parse_one_full_operand(const char **string, int *error) {
char variable_buffer[EVAL_MAX_VARIABLE_NAME_LENGTH + 1];
EVAL_NODE *op1 = NULL;
NETDATA_DOUBLE number;
*error = EVAL_ERROR_OK;
skip_spaces(string);
if(!(**string)) {
*error = EVAL_ERROR_MISSING_OPERAND;
return NULL;
}
if(parse_not(string)) {
op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_NOT, error);
op1->precedence = eval_precedence(EVAL_OPERATOR_NOT);
}
else if(parse_plus(string)) {
op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_SIGN_PLUS, error);
op1->precedence = eval_precedence(EVAL_OPERATOR_SIGN_PLUS);
}
else if(parse_minus(string)) {
op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_SIGN_MINUS, error);
op1->precedence = eval_precedence(EVAL_OPERATOR_SIGN_MINUS);
}
else if(parse_abs(string)) {
op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_ABS, error);
op1->precedence = eval_precedence(EVAL_OPERATOR_ABS);
}
else if(parse_open_subexpression(string)) {
EVAL_NODE *sub = parse_full_expression(string, error);
if(sub) {
op1 = eval_node_alloc(1);
op1->operator = EVAL_OPERATOR_EXPRESSION_OPEN;
op1->precedence = eval_precedence(EVAL_OPERATOR_EXPRESSION_OPEN);
eval_node_set_value_to_node(op1, 0, sub);
if(!parse_close_subexpression(string)) {
*error = EVAL_ERROR_MISSING_CLOSE_SUBEXPRESSION;
eval_node_free(op1);
return NULL;
}
}
}
else if(parse_variable(string, variable_buffer, EVAL_MAX_VARIABLE_NAME_LENGTH)) {
op1 = eval_node_alloc(1);
op1->operator = EVAL_OPERATOR_NOP;
eval_node_set_value_to_variable(op1, 0, variable_buffer);
}
else if(parse_constant(string, &number)) {
op1 = eval_node_alloc(1);
op1->operator = EVAL_OPERATOR_NOP;
eval_node_set_value_to_constant(op1, 0, number);
}
else if(**string)
*error = EVAL_ERROR_UNKNOWN_OPERAND;
else
*error = EVAL_ERROR_MISSING_OPERAND;
return op1;
}
// parse an operator and the rest of the expression
// precedence processing is handled here
static inline EVAL_NODE *parse_rest_of_expression(const char **string, int *error, EVAL_NODE *op1) {
EVAL_NODE *op2 = NULL;
unsigned char operator;
int precedence;
operator = parse_operator(string, &precedence);
skip_spaces(string);
if(operator != EVAL_OPERATOR_NOP) {
op2 = parse_one_full_operand(string, error);
if(!op2) {
// error is already reported
eval_node_free(op1);
return NULL;
}
EVAL_NODE *op = eval_node_alloc(operators[operator].parameters);
op->operator = operator;
op->precedence = precedence;
if(operator == EVAL_OPERATOR_IF_THEN_ELSE && op->count == 3) {
skip_spaces(string);
if(**string != ':') {
eval_node_free(op);
eval_node_free(op1);
eval_node_free(op2);
*error = EVAL_ERROR_IF_THEN_ELSE_MISSING_ELSE;
return NULL;
}
(*string)++;
skip_spaces(string);
EVAL_NODE *op3 = parse_one_full_operand(string, error);
if(!op3) {
eval_node_free(op);
eval_node_free(op1);
eval_node_free(op2);
// error is already reported
return NULL;
}
eval_node_set_value_to_node(op, 2, op3);
}
eval_node_set_value_to_node(op, 1, op2);
// precedence processing
// if this operator has a higher precedence compared to its next
// put the next operator on top of us (top = evaluated later)
// function recursion does the rest...
if(op->precedence > op1->precedence && op1->count == 2 && op1->operator != '(' && op1->ops[1].type == EVAL_VALUE_EXPRESSION) {
eval_node_set_value_to_node(op, 0, op1->ops[1].expression);
op1->ops[1].expression = op;
op = op1;
}
else
eval_node_set_value_to_node(op, 0, op1);
return parse_rest_of_expression(string, error, op);
}
else if(**string == ')') {
;
}
else if(**string) {
eval_node_free(op1);
op1 = NULL;
*error = EVAL_ERROR_MISSING_OPERATOR;
}
return op1;
}
// high level function to parse an expression or a sub-expression
static inline EVAL_NODE *parse_full_expression(const char **string, int *error) {
EVAL_NODE *op1 = parse_one_full_operand(string, error);
if(!op1) {
*error = EVAL_ERROR_MISSING_OPERAND;
return NULL;
}
return parse_rest_of_expression(string, error, op1);
}
// ----------------------------------------------------------------------------
// public API
int expression_evaluate(EVAL_EXPRESSION *expression) {
expression->error = EVAL_ERROR_OK;
buffer_reset(expression->error_msg);
expression->result = eval_node(expression, expression->nodes, &expression->error);
if(unlikely(isnan(expression->result))) {
if(expression->error == EVAL_ERROR_OK)
expression->error = EVAL_ERROR_VALUE_IS_NAN;
}
else if(unlikely(isinf(expression->result))) {
if(expression->error == EVAL_ERROR_OK)
expression->error = EVAL_ERROR_VALUE_IS_INFINITE;
}
else if(unlikely(expression->error == EVAL_ERROR_UNKNOWN_VARIABLE)) {
// although there is an unknown variable
// the expression was evaluated successfully
expression->error = EVAL_ERROR_OK;
}
if(expression->error != EVAL_ERROR_OK) {
expression->result = NAN;
if(buffer_strlen(expression->error_msg))
buffer_strcat(expression->error_msg, "; ");
buffer_sprintf(expression->error_msg, "failed to evaluate expression with error %d (%s)", expression->error, expression_strerror(expression->error));
return 0;
}
return 1;
}
EVAL_EXPRESSION *expression_parse(const char *string, const char **failed_at, int *error) {
if(!string || !*string)
return NULL;
const char *s = string;
int err = EVAL_ERROR_OK;
EVAL_NODE *op = parse_full_expression(&s, &err);
if(*s) {
if(op) {
eval_node_free(op);
op = NULL;
}
err = EVAL_ERROR_REMAINING_GARBAGE;
}
if (failed_at) *failed_at = s;
if (error) *error = err;
if(!op) {
unsigned long pos = s - string + 1;
netdata_log_error("failed to parse expression '%s': %s at character %lu (i.e.: '%s').", string, expression_strerror(err), pos, s);
return NULL;
}
BUFFER *out = buffer_create(1024, NULL);
print_parsed_as_node(out, op, &err);
if(err != EVAL_ERROR_OK) {
netdata_log_error("failed to re-generate expression '%s' with reason: %s", string, expression_strerror(err));
eval_node_free(op);
buffer_free(out);
return NULL;
}
EVAL_EXPRESSION *exp = callocz(1, sizeof(EVAL_EXPRESSION));
exp->source = string_strdupz(string);
exp->parsed_as = string_strdupz(buffer_tostring(out));
buffer_free(out);
exp->error_msg = buffer_create(100, NULL);
exp->nodes = op;
return exp;
}
void expression_free(EVAL_EXPRESSION *expression) {
if(!expression) return;
if(expression->nodes) eval_node_free(expression->nodes);
string_freez((void *)expression->source);
string_freez((void *)expression->parsed_as);
buffer_free(expression->error_msg);
freez(expression);
}
const char *expression_strerror(int error) {
switch(error) {
case EVAL_ERROR_OK:
return "success";
case EVAL_ERROR_MISSING_CLOSE_SUBEXPRESSION:
return "missing closing parenthesis";
case EVAL_ERROR_UNKNOWN_OPERAND:
return "unknown operand";
case EVAL_ERROR_MISSING_OPERAND:
return "expected operand";
case EVAL_ERROR_MISSING_OPERATOR:
return "expected operator";
case EVAL_ERROR_REMAINING_GARBAGE:
return "remaining characters after expression";
case EVAL_ERROR_INVALID_VALUE:
return "invalid value structure - internal error";
case EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS:
return "wrong number of operands for operation - internal error";
case EVAL_ERROR_VALUE_IS_NAN:
return "value is unset";
case EVAL_ERROR_VALUE_IS_INFINITE:
return "computed value is infinite";
case EVAL_ERROR_UNKNOWN_VARIABLE:
return "undefined variable";
case EVAL_ERROR_IF_THEN_ELSE_MISSING_ELSE:
return "missing second sub-expression of inline conditional";
default:
return "unknown error";
}
}
const char *expression_source(EVAL_EXPRESSION *expression) {
if(!expression)
return string2str(NULL);
return string2str(expression->source);
}
const char *expression_parsed_as(EVAL_EXPRESSION *expression) {
if(!expression)
return string2str(NULL);
return string2str(expression->parsed_as);
}
const char *expression_error_msg(EVAL_EXPRESSION *expression) {
if(!expression || !expression->error_msg)
return "";
return buffer_tostring(expression->error_msg);
}
NETDATA_DOUBLE expression_result(EVAL_EXPRESSION *expression) {
if(!expression)
return NAN;
return expression->result;
}
void expression_set_variable_lookup_callback(EVAL_EXPRESSION *expression, eval_expression_variable_lookup_t cb, void *data) {
if(!expression)
return;
expression->variable_lookup_cb = cb;
expression->variable_lookup_cb_data = data;
}
static size_t expression_hardcode_node_variable(EVAL_NODE *node, STRING *variable, NETDATA_DOUBLE value) {
size_t matches = 0;
for(int i = 0; i < node->count; i++) {
switch(node->ops[i].type) {
case EVAL_VALUE_NUMBER:
case EVAL_VALUE_INVALID:
break;
case EVAL_VALUE_VARIABLE:
if(node->ops[i].variable->name == variable) {
string_freez(node->ops[i].variable->name);
freez(node->ops[i].variable);
node->ops[i].type = EVAL_VALUE_NUMBER;
node->ops[i].number = value;
matches++;
}
break;
case EVAL_VALUE_EXPRESSION:
matches += expression_hardcode_node_variable(node->ops[i].expression, variable, value);
break;
}
}
return matches;
}
void expression_hardcode_variable(EVAL_EXPRESSION *expression, STRING *variable, NETDATA_DOUBLE value) {
if (!expression || !variable || isnan(value))
return;
size_t matches = expression_hardcode_node_variable(expression->nodes, variable, value);
if (matches) {
char replace[1024];
snprintfz(replace, sizeof(replace), NETDATA_DOUBLE_FORMAT_AUTO, value);
size_t replace_len = strlen(replace);
size_t source_len = string_strlen(expression->source);
const char *source_str = string2str(expression->source);
// Allocate enough space to accommodate all replacements.
char buf[source_len + 1 + matches * (replace_len + 1)];
char find1[string_strlen(variable) + 1 + 1];
snprintfz(find1, sizeof(find1), "$%s", string2str(variable));
size_t find1_len = strlen(find1);
char find2[string_strlen(variable) + 1 + 3];
snprintfz(find2, sizeof(find2), "${%s}", string2str(variable));
size_t find2_len = strlen(find2);
size_t found = 0;
char *buf_ptr = buf;
const char *source_ptr = source_str;
while (*source_ptr) {
char *s1 = strstr(source_ptr, find1);
char *s2 = strstr(source_ptr, find2);
char *s = s1;
size_t len = find1_len;
if (s2 && (!s1 || s2 < s1)) {
s = s2;
len = find2_len;
}
if (s) {
if (s == s1 && (isalnum((uint8_t)s[len]) || s[len] == '_')) {
// Move past the variable if it's part of a larger word.
source_ptr = s + len;
continue;
}
// Copy the part before the variable.
memcpy(buf_ptr, source_ptr, s - source_ptr);
buf_ptr += (s - source_ptr);
// Copy the replacement.
memcpy(buf_ptr, replace, replace_len);
buf_ptr += replace_len;
*buf_ptr = '\0';
// Move the source pointer past the replaced variable.
source_ptr = s + len;
found++;
} else {
// Copy the rest of the string if no more variables are found.
strcpy(buf_ptr, source_ptr);
break;
}
}
// Update the expression source with the new string.
string_freez(expression->source);
expression->source = string_strdupz(buf);
}
}